Cohesiwe crack model for geomaterials: Stability analysis and rate effect

The cohesive (or ficticious) crack model, characterized by softening stress-clisplace-ment relations, provides a good description of fracture of quasibrittle materials such as conrete, rock, or tough ceramics. The cohesive crack model is formulated 111 terms of compliance influence functions and the failure is analyzed as a stability problem. The size effect is determined by means of an eigenvalue problem. In this problem, the structure size for which a given relative crack length yields the maximum load is the eigenvalue. The model is further generalized to time dependence. The opening displacement is considered as a function of the cohesive stress and the opening rate of the crack. Finally, applications to rock and concrete are discussed.